Docker Interview Questions

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1. What is a Docker?

A Docker is defined as the platform for containerizing the applications to isolate it from each other in order to ensure high availability and more efficiency irrespective of the environments such as Development, Testing or Production. All the application related dependencies such as libraries, jar files, server related configurations, infrastructure-related elements will be packaged and formed as container called containerized application which does not need any dependency and works independently. It ensures the application to be run irrespective of the external factors. Container in Docker have support from Docker Engine and Host Operating System to support all the operational or infrastructural related dependencies.

2. What are the components of Docker Architecture and explain?

This is the common laborer Interview queries asked in Associate in Nursing interview. The Docker works on client-server architecture. The laborer consumer establishes communication with the laborer Daemon. The laborer consumer and Daemon will run on an equivalent system. A Docket client can also be connected to a remote Docker Daemon. The different varieties of laborer parts in a very laborer design AR

Docker Client: Performs Docker build pull and run operations to building communication with the Docker Host. The laborer command uses laborer API to decision the queries to be run.

Docker Host: Component contains Docker Daemon, Container and its images. images will be the kind of metadata for the applications which are the containerized in the container. The Docker Daemon build a connection with Registry.

Registry: component will be storing the Docker images. The public registries Ar laborer Hub and laborer Cloud which may be s employed by anyone.

A dock-walloper instrumentation could be a type of encapsulation to the appliance that holds all the dependencies that share the kernel with alternative containers within the period of running the isolated processes on the host package. A dock-walloper instrumentation are often created by making a dock-walloper image. These dock-walloper pictures are often run at that time exploitation dock-walloper commands. dock-walloper containers area unit the instances of the dock-walloper pictures at the run time. dock-walloper pictures are often keep in any public hosts or personal hosts like dock-walloper hub. dock-walloper Image could be a set of files which may be run in associate degree isolated method.

4. What are Docker Image and Docker Hub?

The dockhand Image may be a set of files Associate in Nursing a mixture of parameters which is able to enable making the instances to run in separate containers as an isolated method. The dockhand hub may be a reasonably repository to pictures|the pictures|the photographs} wherever these images will be hold on and this access is public. The dockhand run command will be wont to produce the instance known as instrumentality which might be run victimization the dockhand image. Docker hub is that the largest public repository of the image containers that is being maintained by the community of developers and individual contributors.

5. What are the different functionalities and applications of using Docker?

types of functionalities and applications of using and implementing Docker are as below:

It simplifies the configuration and provides ease at infrastructure level configuration.

It manages the code pipeline easily which provides a constant environment and balance in the application.

It enables the isolation of the application.

It improves the productivity of the developer by allowing the developer to solely concentrate on business logic.

It enables a lot of debugging capabilities that provides extreme useful functionalities to implement.

It enables rapid deployment in the form of virtualization at the operating system level.

It reduces the utilization of multiple servers in the form of containerization.

6. What is a Docker Registry?

A stevedore written record may be a place wherever all the stevedore pictures are going to be hold on and stevedore Cloud and stevedore Hub area unit the general public registries wherever these pictures will be hosted upon. The stevedore hub is that the default storage for the stevedore pictures. An own written record also can be came upon as per the necessity. Docker knowledge Center (DDC) also can be used which incorporates DTR (Docker trustworthy Registry). Docker store can give the feature of shopping for and merchandising the stevedore pictures.

7. What is the life-cycle of Docker Container?

This is the most popular Docker Interview Questions asked in an interview. The life cycle of the Docker container is as below:

The stevedore Objects area unit stevedore pictures, Services, and stevedore Containers. A stevedore Image could be a read-only guide with the configuration or run time directions for the stevedore instrumentation. The Services enable scaling the containers across the various stevedore Daemons. These all together work as Swarm.

9. What are Docker Namespaces?

The Namespaces in loader could be a technology that provides isolated work-spaces referred to as the instrumentality. Namespaces give a layer of isolation for the loader containers.

10. What are the important Docker commands?

dockerd To launch Docker daemon.build To build an image file for docker.create To create a new container.kill To kill a container.commit To create a new image from container changes.

11. How is Docker different from other container technologies?

According to Maine, below, points ought to be there in your answer:

Docker containers square measure simple to deploy in a very cloud. It will get a lot of applications running on constant hardware than different technologies, it makes it simple for developers to quickly produce, ready-to-run containerized applications and it makes managing and deploying applications much easier. You can even share containers with your applications.

If you have some more points to add you can do that but make sure the above the above explanation is there in your answer.

12. What is Docker Swarm?

You should start this answer by explaining Docker Swarm.

Docker Swarm is native clustering for Docker. It turns a pool of manual laborer hosts into one, virtual manual laborer host. Docker Swarm serves the quality manual laborer API, any tool that already communicates with a manual laborer daemon will use Swarm to transparently scale to multiple hosts.

I will also suggest you to include some supported tools:

Dokku

Docker Compose

Docker Machine

Jenkins

13. What is Dockerfile used for?

This answer, per Pine Tree State ought to begin by explaining the employment of Dockerfile.

Docker will build pictures mechanically by reading the directions from a longshoreman file.

Now I will suggest you to give a small definition of Dockerfle.

A Dockerfile may be a text document that contains all the commands a user may invoke the instruction to assemble a picture. Using longshoreman build users will produce an automatic build that executes many command-line directions in succession.

14. Can I use json instead of yaml for my compose file in Docker?

You can use json instead of yaml for your compose file, to use json file with compose, specify the filename to use for eg:

docker-compose -f docker-compose.json up

15. Tell us how you have used Docker in your past position?

Explain however you’ve got used lumper to assist speedy preparation. Explain however you’ve got written lumper and used lumper with different tools like Puppet, cook or Jenkins.If you’ve got no past sensible expertise in lumper and have past expertise with different tools in a very similar house, be honest and justify an equivalent. In this case, it is sensible if you’ll compare different tools to lumper in terms of practicality.

16. How to create Docker container?

I will suggest you to give a direct answer to this.

We can use Docker image to create Docker container by using the below command:

1 docker run -t -i command name

This command will create and start a container.

You should also add, If you want to check the list of all running container with the status on a host use the below command:

1 docker ps -a

17. How to stop and restart the Docker container?

In order to stop the Docker container you can use the below command:

1 docker stop container ID

Now to restart the Docker container you can use:

1 docker restart container ID

18. How far do Docker containers scale?

Large net deployments like Google and Twitter, and platform suppliers like Heroku and dot Cloud all run on instrumentality technology, at a scale of many thousands or maybe millions of containers running in parallel.

19. What platforms does Docker run on?

I will start this answer by saying Docker runs on only Linux and Cloud platforms and then I will mention the below vendors of Linux:

Ubuntu 12.04, 13.04 et al

Fedora 19/20+

RHEL 6.5+

Cent-OS 6+

Gentoo

Arch Linux

open SUSE 12.3+

CRUX 3.0+

Cloud:

Amazon EC2

Google Compute Engine

Microsoft Azure

Rackspace

Note that Docker does not run on Windows or Mac.

20. Do I lose my data when the Docker container exits?

You can answer this by saying, no I won’t lose my data when Docker container exits, any data that your application writes to disk gets preserved in its container until you explicitly delete the container. The file system for the container persists even after the container halts.

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